"Fear of the unknown does not mean the unknown needs to be feared"
Exactly!

The purveyor of the cam and race engine/bike builder has not come across this in over 30 years of building race winning Ducati single motors that have won the Manx etc, etc, etc. My 'Mix 'n Match' tuning missed out on the latter!

Rather than trying to do a 'paddock' cam change, I've decided to lift the head and then change the cam, re-shim the valve/rocker clearances, before re-assembling and then testing. My cam holder is not a snug fit and the flexing as I apply 35ft/lb through the cam nut is not a pretty sight, causing the helical bevel gears to flex!

Helical bevel gear pair replacements are as rare as rocking horse sh1te and a set of straight cut replacements start at over £600, if I break a helical tooth.

If the cam change makes a difference, then the next step is to lift and strip the head again, rough up the inlet port with 120 grit emery and the exhaust port with 60 to 80 grit emery, replace the 'White' cam, with the 173A and see if the problem returns! If it does, it would appear that the valve overlap is too much for my engine and I will strip again and install the 'White' cam for keeps.

Hope the Himalaya is good, I have a friend who thinks they are the best since sliced bread.
As for the "Sainthood", no this is part of the family that just needs a bit of TLC to go cantering again.

Good health, Bill